Pulse oximeters are non-invasive medical devices configured to determine peripheral oxygen saturation (SpO2). In particular, pulse oximeters measure a ratio of the optical absorption of two forms of hemoglobin, oxyhemoglobin and deoxyhemoglobin, in blood. The amount of absorption of hemoglobin measured in the blood may then be used to determine the peripheral oxygen saturation SpO2.
Pulse oximeters operate on the principle of spectrophotometry, using wavelengths of light to determine the concentration level of oxygen in blood. Typically, pulse oximeters include a clamping probe that clamps around a translucent part of a patient's tissue, such as a finger. One side of the clamping probe includes light emitting diodes (LEDs) for emitting radiation at two distinct wavelengths towards the patient's tissue, and the other side of the clamping probe includes a photodiode aligned with the LEDs to receive the radiation that transmits through the patient's tissue. The amount of radiation for each wavelength that is received by the photodiode is measured.
Pulse oximeters distinguish between pulsating peripheral blood (AC components) and non-pulsating tissue (DC components). A ratio of the AC component of absorbency for each wavelength and the DC component of absorbency at each wavelength is then used to determine the peripheral oxygen saturation SpO2 in the patient's blood using known radiation absorption levels of hemoglobin in blood.
In order to verify a pulse oximeter's operation, pulse oximeter testers have been used to test the quality or reliability of the measurements made by the pulse oximeter.